Unexplained acute fever after a hot bath.

An outbreak of repeated chills, fever, respiratory-tract symptoms, and muscle pain, starting 4 h after a hot bath, involved 56 persons, nearly all of whom lived in an area supplied with water from the same source. The symptoms lasted for 6--15 h. A polymorphonuclear leucocytosis was a feature of the illness. The causal agent, which has not yet been identified, was found to enter the body by inhalation. Bacteriological and chemical studies and investigation of the water for endotoxins and algae revealed nothing unusual.